Fiber optic reading magnifiers

ABSTRACT

A reading magnifier formed by a bundle of juxtaposed longitudinally tapered optical fibers having a viewing end and a flat base end. The flat base end is cut at a bias across the bundle of optical fibers such that a line normal to the flat base end forms an acute angle with the direction of orientation of the optical fibers. The viewing end of the bundle may also be cut at an angle relative to the optical fibers. The reading magnifier provides a cone of light admittance that is skewed at an angle relative to a cylinder normal to the flat base end. The tilted admittance cone may also be achieved by bending the bottom portion of a bundle of tapered continuous optical fibers.

BACKGROUND OF THE INVENTION

This invention is related to a magnifying apparatus, and moreparticularly, to an apparatus and method used to view an object such asa book or other printed material on a surface by magnifying the image ofthe object and viewing the magnified image at a convenient angle to thesurface on which the object is located. Specifically, this invention isrelated to the use of fiber optic tapers as magnifiers. Stand magnifiersare frequently used as a visual aid by the visually impaired. Their mainadvantage over other reading aids is their relative stability and easeof use. The fixed and stable distance from the reading material, and theflexibility in distance from the eye to the magnifier make their useeasy to learn.

Most existing stand magnifiers, however, require the user to bend overthe magnifier in order to be able to read through them. When used at adesk, for example, the user has to lean forward and closely follow, withhis/her whole upper-body, the position of the magnifier on the page.

The postural problem with the stand magnifier also complicates theattainment of proper illumination for the printed material. The user'shead tends to block light from above, and thus the need to permit lightaccess through the sides of the magnifier which makes for anuncomfortable and difficult hand grip. The difficulties in gettingproper illumination have resulted in the development of manyelectrically powered illuminated stand magnifiers. As one solution tothese difficulties, Combined Optical Industries Limited (COIL), 200 BathRoad, Slough, SL14DW, England, has recently introduced a series oftilting stand magnifiers (Coil 5214). However, tilting the lens resultsin distortions and reduces the field of view. U.S. Pat. No. 4,923,282(Spitzberg et al.) discloses another attempt to address this issue witha design that incorporates a prism to tilt the image's angle,

As with all other lens magnifiers, the stand magnifiers are limited alsoby distortions and vignetting. In most cases, the limited field preventsbinocular use and thus eliminates the potential benefits of binocularvision. Attempts to increase the field by aspheric lens design usuallyfurther increase the optical distortions.

The actual magnification provided by lens magnifiers is not easilydefined or measured. The information provided by the manufacturer isfrequently inaccurate and misleading (Bullimore and Bailey, Standmagnifiers: an evaluation of new optical aids from COIL, Optometry andVision Science, 66; 766-773, 1989), thus making the use and prescriptionof these devices unnecessarily complicated.

As an entirely different approach a symmetrical bundle of taperedoptical fibers (commonly referred to as a taper) such as that shown inFIG. 1 has been used as a magnifier. The most common application hasbeen for use by stamp collectors. The image light from these magnifiersis directed for the most part perpendicular to the viewing face makingthe best viewing position directly over the magnifier. While a user maytolerate bending over the magnifier to view a stamp, it would be veryawkward for extended use in reading a book, for example. Furthermore,these symmetrical optical fiber tapers provide no control over unwantedspecular reflection.

There is, therefore, a need for a magnifier which does not introducedistortion and which can be used by a person sitting in an uprightposition, and which does not require the person to bend over theapparatus when reading a full page of text.

SUMMARY OF THE INVENTION

The invention is directed to a reading magnifier formed from a bundle ofjuxtaposed longitudinally tapered optical fibers. The viewing end of theoptical fiber bundle is at the larger end. The opposite (smaller) end ofthe bundle is flat. This flat base end is cut at an angle with respectto the optical fibers such that a line normal to the flat base end formsan acute angle with the direction of orientation of the optical fibers.The viewing end may also be cut at an angle, in particular, such thatthe viewing end is parallel or almost parallel with the flat base end ofthe bundle. The viewing end may be further modified to include a convexspherical or cylindrical surface. In order to serve as a readingmagnifier, low resolution fibers having a diameter at the viewing end ofat least about 80 microns are acceptable for users with normal vision.

An alternate embodiment of the reading magnifier of the invention may beformed in which continuous fibers are curved between the flat base endof the bundle and the large (viewing) end of the fibers. Moreover, aconstant diameter portion may extend between the viewing end of thebundle and the tapered portion of the fibers.

The reading magnifier of the present invention may be advantageouslymanipulated with ease by the user to increase the use of available lightsources for illuminating the magnified image and to reduce or eliminatespecular reflections. Further advantages of the reading magnifier of theinvention are that it provides a large scanning range and that it can beviewed by more than one person thereby facilitating the teaching ofreading with magnifiers to the visually impaired. The reading magnifiersof the present invention advantageously have a cone of light admittancethat is skewed relative to vertical (when placed on a horizontalsurface) so that simple rotation of the magnifier can optimizeillumination and/or decrease glare.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing of a prior art tapered fiber optic bundle being usedas a reading magnifier.

FIG. 2 is an illustration of the prior art magnifier of FIG. 1illustrating the range of positions of a user's eyes from which the textcan be seen with the magnifier.

FIG. 3 is a side view of one embodiment of a reading magnifier of thepresent invention.

FIG. 4 is an illustration of the reading magnifier of FIG. 3demonstrating the scanning range relative to a person sitting at a flatsurface such as a desk.

FIG. 5a is a side view of an alternate embodiment of the readingmagnifier of the invention.

FIG. 5b is a side view of a second alternate embodiment of the readingmagnifier of the invention.

FIG. 6a and 6b illustrate one method for making the tapered magnifiersof the invention.

FIG. 7 is an illustration of a method step for making the readingmagnifier of the alternate embodiment illustrated in FIG. 5.

FIG. 8 is a diagram illustrating the concept of the expanded admittancecone.

FIG. 9 is a side view of another embodiment of the present invention inwhich the viewing end and flat base end of the reading magnifier areparallel to one another.

FIG. 10 is a side view of a still further embodiment of the inventionwherein the bundle of optical fibers has a constant diameter portionadjacent the viewing end.

FIG. 11 is a diagram illustrating the ideal tilt angles cut through abundle of tapered optical fibers for limiting distortions.

FIG. 12 is an illustration of the admittance cone and the control ofspecular reflections associated with a reading magnifier cut inaccordance with FIG. 11.

FIG. 13a is a diagram illustrating the chief ray tilted towards the userat the large face of a magnifier illustrated in FIG. 10.

FIG. 13b is a diagram illustrating the change in chief ray light tilt atthe viewing face of a magnifier that has been cut across a taperedportion of a bundle of optical fibers.

FIG. 14 is a side view of a still further embodiment of the invention inwhich the viewing face is a convex surface.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This invention relates to a magnifying apparatus, and more particularly,to fiber optic magnifiers. It is well known that a tapered fiber opticbundle containing well-aligned (so called "coherently" aligned) fibersis capable of transmitting an image from one face to the opposite facewith either a reduction or magnification in size. Specifically, the sizeof the transmitted image is in direct proportion to the change of sizeof the two ends of the fiber optic taper. Size ratios (i.e.magnifications) of from nearly unity to as much as 10:1 may bepractically obtained using a fiber optic taper.

When the small end of the taper is placed in contact with an object suchas a printed page, an enlarged image appears at the upper, larger faceof the taper (FIG. 1). Moreover, light entering the upper face fromceiling lamps, the sun or any light source generally located above thetaper is captured by the taper and is "condensed" onto the objectsurface and serves to illuminate the object. In general, no additionalillumination is needed under normally illuminated ambient conditions.For maximum light gathering capability, the optical fibers making up thetaper should have a high effective numerical aperture.

Numerical aperture (N.A.) is defined as:

    N.A.=n sin α

where n is the refractive index of the external medium (normally airwhere n=1.0) and α is the half angle of the largest cone of lightcapable of entering or leaving the fiber. In a fiber optic taper, theN.A. is a maximum at the smaller end: ##EQU1## where n₁ is therefractive index of the core of the fiber, and n₂ is the refractiveindex of the cladding of the fiber.

At the larger end, the effective N.A. is reduced by virtue of thetapering of the fibers and the enlarging of the image in a mannersimilar to the Lagrange condition for lenses. Thus, the effective N.A.of the large end of the taper is:

    N.A..sub.EFF =N.A.(max.)/M,

where M is the taper ratio or magnification.

For the best light gathering capability and large scanning range, thiseffective N.A. should be relatively large, in the range of 0.2-0.5. Ifthe small end N.A. (max.) is nearly 1.0 then values of M of 2x-5x arepractical.

The size of the fibers in the taper is determined by the application asa visual magnifier. In general, the large end of the taper will beviewed by the naked eye at about 10 inches away (or a range of 6"-20",depending on the accommodation capabilities of the observer). At adistance of 10 inches and with normal eye resolution of about 1/3milliradian, the diameter of the fibers at the large end can be about0.0033 inches (or about 80 μm) and be just barely resolved by one withnormal vision. As a practical matter, the image with the taper will alsobe visually acceptable with a fiber size of 2-3 times this value (up to160-240 μm in size).

When used by persons with impaired vision (due to macular degeneration,for example), the fiber size may be even larger and be entirelyeffective. Fiber sizes up to 500 μm may be entirely adequate dependingupon the degree of limited visual capabilities of the observer.

These large fiber sizes which are suitable for magnifiers for visuallyimpaired persons allow the manufacturing process for these tapers to besimplified, thereby reducing their cost of manufacture.

The present invention makes use of these properties of fiber optictapers as reading magnifiers, but, in addition, improves upon their useby slanting either the bottom face or both faces of the taper so as totilt the light emitted from the upper face towards the eye of theobserver, when seated at a table for example.

In a prior art fiber optic magnifier 20, the image seen on the upperface 22 may be viewed at a small angle to that face and still be clearlyseen, but due to reduction in N.A. resulting from tapering, this angleis quite limited and thereby limits the scanning area for the magnifier.This scanning area is the range over which an eye can see the image onthe upper face 22 as shown in FIG. 2. In the prior art fiber opticmagnifier 20, the upper face 22 and the bottom face 24 are perpendicularto the straight coherent orientation direction of the optical fibers.

One way in which the scanning area may be increased and made morecomfortable for the viewer is by tilting the output face of the bundleof fibers taper toward the viewer. This can be done by cutting andsurfacing the input or small face of the bundle at an angle to the axisas shown in FIG. 3. The reading magnifier 30 of FIG. 3 has a viewingface 32 that is perpendicular to the fused bundle of juxtaposedlongitudinally tapered optical fibers. The fibers of the bundle aretightly juxtapositioned and coherently aligned. The flat base input end34 of the solid bundle is cut on a bias angle across the bundle. Theangle can be defined as an acute angle formed between a normal 40 to theflat base end 34 and an orientation direction 38 of the optical fibers.The orientation direction 38 is generally defined by a longitudinal axisthrough a straight centrally located fiber in the solid fiber bundle.The amount of the bias angle along with the effective N.A. of the bundlewill determine the scanning range of the magnifier (FIG. 4). This rangemay be calculated as follows: ##EQU2##

For the nominal case where D=O, the taper magnifier is scanned from justunder the eyes and away from the observer. For this case the optimaltilt angle is θ=α. Smaller angles will result in a loss of scanningrange (expressed as negative D values in Table 1). The effective(useful) range is the range L minus any negative portion of the measureD. Angles of tilt larger than α are possible but will force the scanningrange away from the user (D>O). A small positive value for D such as 1-2inches is probably best for the reading task. Table 1 compares thecalculated scanning field for a number of tapers parameters, andillustrate the increases in the effective scanning range resulted fromthe introduction of a tilt.

                                      TABLE 1    __________________________________________________________________________    The effective scanning field calculated for a number of tapers. In all    cases height of    eye is object is H = 10".    NA (nominal)           Mag (M)                α = admittance                        θ = Tilt                             L   D   Effective Range    __________________________________________________________________________    1.0    3.0X 19.47°                         0°                             7.07"                                 -3.54"                                     3.54"    1.0    3.0X 19.47°                           19.47°                             8.08                                 0"  8.08"    1.0    3.0X 19.47°                        25°                             8.85"                                 0.97"                                     8.85"    1.0    2.5X 23.58°                         0°                             8.73"                                 -4.36"                                     4.36"    1.0    2.5X 23.58°                        30°                             12.43"                                 1.13"                                     12.43"    0.66   2.5X 15.31°                         0°                             5.47"                                 -2.74"                                     2.74"    0.66   2.5X 15.31°                        20°                             6.26"                                 .82"                                     6.26"    1.0    2.0X 30°                         0°                             11.55"                                 -5.77"                                     5.77"    1.0    2.0X 30°                        36°                             21.41"                                 1.05"                                     21.41"    __________________________________________________________________________

The lateral scanning range is also limited by the effective range. Byslightly rotating the slanted taper (towards the user) while scanninglaterally, the lateral range can be maximized. The full scanning fieldcovered this way will be bound by a circle of radius equal to thescanning range (L+D), center at the observer. Thus for D=O, for most ofthe forward field (up to 85%) a lateral field wider than the scanningrange (L) may be covered.

Cutting the smaller face of the bundle at an angle (FIG. 3) willintroduce a small amount of an anamorphic magnification into the imagedisplayed on the large face. That is, the magnification will bedifferent for the vertical and horizontal meridians (diameters) of thetransmitted image. The amount of this difference (more correctly theratio of these magnifications) is simply the cosine of the angle of cutrelative to the normally (perpendicular) face (FIG. 3) (angle θ). For arelatively large angle of cut of θ=30° in the above examples, cos30°=0.87, so that only 13% anamorphic magnification results. For a moretypical value of θ=20° (cos 20°=0.94), the ratio is 0.94 which isscarcely noticeable. This anamorphic magnification causes the verticalmagnification of the scanned text to be slightly less than thehorizontal so that enlarged objects appear slightly wider (or less high)than normal when viewed with the tilted bundle 30. Even this smalldifference can be reduced or eliminated in a number of ways as shownbelow.

If the cut through the small end of the magnifier is made through thetapered portion of the magnifier an additional type of distortion willresult, namely "Keystone" distortion. When cut through the taperedportion, different regions of the upper taper face provide differentmagnifications. The region closer to the user provides lessmagnification than the region further away from the user. The level ofdistortion depends both on the angle of cut and on the steepness of thetapering at the level of the cut. This distortion is not particularlyserious, however, because when the magnifier is used for reading, eachline of text has a uniform magnification and the difference between themagnification of adjacent lines is small and unimportant.

One method for eliminating all anamorphic magnification or keystone likedistortion is to "bend" the smaller end of the bundle as shown in FIG.5a. The reading magnifier 40 of FIG. 5a is a solid bundle of tightlyjuxtapositioned longitudinally tapered optical fibers. The flat base end44 of the bundle is perpendicular to the longitudinal orientation of theoptical fibers at the intersection with the flat base. The bundle has atapered portion 48 in which the optical fibers increase in diameter fromthe base end 44 towards the wide end of the bundle. The tapered portion48 is bent or curved near the flat base end 44. The fibers in thetapered portion 48 are continuous fibers that have been bent or curved.A viewing face 42 may be cut across the tapered portion 48 perpendicularto the orientation direction of the optical fibers. Alternatively, aconstant diameter portion of the optical fibers 49 may be providedbetween the tapered portion 48 and viewing face 42.

A combination of both bending and bias cutting may be employed to tiltthe magnifier toward the user. The desired tilt can be achievedpartially from a smaller angle bend and partially from a smaller anglebias cut as illustrated in FIG. 5b. Such a magnifier 100 has a taperedportion 108 and may optionally include a constant diameter portion 109adjacent the viewing face 102. The tapered portion 108 has a partialbend near the small base end 104. The base end 104 is cut at a biasangle relative to the orientation direction of the optical fibers in thebundle adjacent to the base end. The bias cut shortens the fibers at theinner radii of the bend in the bundle. The bias cut therefore adds tothe tilt of the magnifier begun by the bend. By combining a bend and abias cut, a more stable magnifier than one achieved only through bendingcan be achieved. The smaller angle of bending may result in easierproduction and reduced distortions. Similarly, the partial bend reducesthe needed angle for the bias cut resulting in a reduction indistortions associated with such a cut.

Tapering and bending of a fused bundle of optical fibers can be achievedin either a single or a combination of forming steps by softening thefiber bundle at an appropriate temperature in an electric furnace asshown in FIG. 6a. The usual tapering process is done by heating thecentral region of a cylindrical bundle or boule of fused optical fibersand pulling the heat softened boule into an hourglass shape as shown inFIG. 6b. Bending of the dual taper can then be achieved by tilting oneend relative to the other as shown in FIG. 7 either as part of the sameheating cycle or as a separate operation. In either case, if theoperation is carried out with symmetrical forces and heat distribution,two essentially identical tapers can be made from the starting boule.The curved bundle is cooled to a solid inflexible state. The bundle maythen be cut across the central region forming two magnifiers. In use,the bend in the reading magnifier 40 will tilt the magnifier towards theuser to provide the increased scanning range and will not suffer fromthe distortions of a bias angle cut through the bottom, smaller end.

In addition to providing an increased scanning range these tilted fiberoptic magnifiers, of both types described above, also provide bettercontrol of illumination, both for the purpose of collecting the ambientlight and in avoiding the glare resulting from specular reflections ofany bright light sources from the upper viewing face of the bundle. Dueto the tilt of the upper face, rotation of the magnifier around avertical axis permits the user to include within the magnifier'sadmittance cone a light source (a window or a ceiling light fixture)which would otherwise be outside the admittance cone of the same taperwithout the tilt (FIG. 8). A prior art bundle of tapered optical fibers20 with perpendicular top and bottom faces has a cone of admittancewhich is symmetrical about a center axis. Rotation of the prior artbundle 20 does not alter the location of the cone of admittance. Once alight source lies within the admittance cone its light is concentratedby the tapered fibers and results in a brighter image. Specularreflections from bright sources which would be reflected from thepolished upper surface of the magnifier can also be redirected with themagnifiers of the invention by the same slight rotation of the magnifierto tilt the reflections off the viewing face away from the user's eyes.

A second method for reducing or eliminating the anamorphic and keystonelike distortion of the taper bias cut at the smaller end involves asecond substantially parallel cut of the taper at the large viewing end62 as shown in FIG. 9. In accordance with this alternate embodiment, abundle of tightly juxtapositioned longitudinally tapered optical fibers60 is cut at a bias angle across its small end to form a flat base end64. Substantially the same bias angle is used to cut across the opticalfibers at the larger end to form the viewing face 62. A line normal 66to the flat base end 64 makes the acute bias angle with a line in theorientation direction of the optical fibers in the bundle 60. Theorientation direction of the fibers is generally defined by a straightoptical fiber located in the center of the bundle 60.

The main purposes of the bias cut to form the viewing face 62 are todirect the viewing face of the bundle so as to provide a more convenientand comfortable viewing position for the viewer, and to distribute theoutput light to achieve a maximum scanning range over the object (suchas a printed page), and to provide better control over collecting lightfrom sources in the user's environment. Effectively, the fibers' tipsare cut at an angle forming prisms. At the same time the bias cut of thetop face also may be used to reduce or eliminate the anamorphicmagnification.

The relation of the angle of cut at the large end to the angle of cut atthe smaller end needed to correct for the anamorphic and keystonedistortions can be calculated for simple cases and easily approximatedfor other conditions. For the case of a bundle of ideal conical shape(where both cuts are made through the conical portion) they should beparallel to eliminate both types of distortions (FIG. 9). In any case,the angle of the cut at the large end should be similar to the angle ofcut at the small end relative to perpendicular to orientation directionof the fibers. If not equal, it is preferred that the amount of theangle of the cut of the large end be smaller than the cut at the smallend, so that the magnifier view face is tilted towards the user.

For a bundle 70 with a conical tapered portion 77, where the top of thebundle is blended into a cylindrical untapered constant portion diameter(FIG. 10) the effect is different. If the bias cut at the large viewingend 72 is made above the tapered portion 77 the keystone distortion willnot be affected by this cut at any angle. On the other hand theanamorphic magnification can be eliminated by this cut at an angle φwhere ##EQU3## where ω is the angle of the conical taper (angle betweenthe outer wall of the tapered portion 77 and the orientation directionof the fibers) and θ is the bias angle of the cut at the small base end74 of the bundle.

Most practical fiberoptic tapers are not exactly conical in shape.Complete elimination or major reduction of the keystone distortion canbe achieved with any shape of taper by bias cutting the top surface ofthe magnifier through the tapered portion at such an angle that thechange in taper diameter across the cut will be at the same ratio as thechange of the taper diameter across the bottom cut. As shown in FIG. 11,once the bottom face was cut at a given angle, defining the twodiameters D₁ and D₂, the top face has to be cut down to a level on thetaper defined by taper diameter D₃ such that Another way to state thedesired relationship is that the cut ##EQU4## should be such that localmagnification or the ratio of fiber diameters at the corresponding edgeswill be equal, i.e., the fiber diameter at 84 will be the same ratio todiameter at 82 as is diameter at 83 to 81.

The bias cut of the top face also results in directing the lightemerging from the bundle towards the user (as explained below) and thusreduces the magnitude of the angle of the bias cut needed at the smallerend. The smaller the angle of cut at the small end the less themagnitude of distortions resulting therefrom.

The bias cut at the large viewing end 62 is used to direct the lighttoward the user. This is due to the prismatic effect at the tip of eachfiber i.e. the light emerging from the center of each fiber passes(refracted) at an angle through a glass air interface. With the anglecut, the light emerging at the center of each fiber passes through aglass air interface at an angle. This refraction tends to cause emergingrays to deviate towards the user as shown by angle λ' in FIG. 9. Theoptimal deviation or tilt of the axial ray from the vertical is slightlymore than the admittance half angle α determined by the NA. With thislevel of tilt the same condition of slightly positive range D describedabove will be achieved. The tilt of the axial ray due to the bias cut ofthe top face is close to twice the cut angle. For a fiber core glasswith index n=1.8, a cut of the viewing face at angle λ' will result inthe axial ray in the air shifted at angle to the normal where

    sin λ'=1.8 sin λ

Therefore, a combined parallel cut of both surfaces of the taper atangle λ will result in an axial ray tilt of about 2λ from the vertical.The fibers will arrive at the top at an angle of λ and the top face cutwill shift the ray about 2λ from the normal which is now vertical again.Thus, optimal tilt can be achieved by cutting both the bottom and topfaces at angles ##EQU5## This smaller angle of cut reduces the level ofanamorphic magnification effect and the keystone type distortion to anegligible level.

In addition to reducing distortion and therefore also preservingmagnification, the cut at the top of the taper combined with the nearlyparallel cut at the bottom permits better control of the lightcollection and specular reflections. The cone of light admittance isskewed at an angle relative to vertical as shown in FIG. 12 for apractical tapered bundle 80. With this design the bundle can be usedeffectively with illumination coming over the user's shoulder onto thepaper. This illumination arrangement is recommended for visuallyimpaired and for comfortable reading in general to prevent glare fromthe source from reaching the user's eyes. A bundle 80 cut as describedabove will have a flat top viewing surface 62 parallel to the desk,therefore, specular reflections from light sources behind the user willbe reflected away from the user's eyes.

Although the top surface of the taper is horizontal its admittance coneis tilted relative to vertical. Vertical being established by a normalto the flat base end 64. (FIG. 12). Thus the position of the admittancecone in space can be controlled by slight rotations of the bundle, as ispossible with the tilted viewing end of the above-described embodiments,to scan the environment for better collection of light from ambientsources.

If the cut through the top surface is made through the tapered portion,the amount of light tilt will vary across the viewing face asillustrated in FIG. 13b. The light emerging from the region of theviewing face for positioning closer to the user will be tilted moretowards the user than light emerging from the center of the viewingface.

    λ">λ'

This is the result of the combined overall taper tilt and the inherenttilt of fibers on the outside portion of the bundle. On the other hand,at the region of the viewing face to be positioned further from theuser, the light will be bent the least since the prismatic effect due tothe taper tilt will cancel the inherent fiber tilt. It may actually bebent away from the user but the angle of deviation from the normal issmaller there.

    λ'>λ'"

Thus the deviation at that region of the viewing face away from theobserver will be reduced as is preferred. The tilt of the light acrossthe viewing face may be favorably controlled even further by forming thetop surface as a convex surface 92 of either spherical shape or ofcylindrical shape with horizontal axis perpendicular to the front toback direction of the slant cut across the top of the bundle 90, asshown in FIG. 14. With such a convex surface the amount of localprismatic effect at both the near and far regions of the top face may bereduced to counter the change in fiber angles at the edges of the taper.

Of course, it should be understood that various changes andmodifications to the preferred embodiments described above will beapparent to those skilled in the art. For example, the bias angleselected for cutting the flat base end and viewing end may differ aswell as the differences in the degree of taper of the optical fibers.Also, the shape of the reading magnifier may be changed to suit thedesirability of the final product for handling by the user of themagnifier. These and other changes can be made without departing fromthe spirit and scope of the invention and without diminishing itsattendant advantages. It is therefore intended that such changes andmodifications be covered by the following claims.

I claim:
 1. A reading magnifier comprising:a bundle of juxtaposedlongitudinally tapered optical fibers having a large end and a flatsmall end, said optical fibers each having a larger diameter at thelarge end than proximate the flat small end, said bundle of opticalfibers being coherently aligned along an orientation direction definedby a longitudinal axis through a straight centrally located opticalfiber in said bundle, wherein a line normal to the flat small end formsan acute angle with the orientation direction.
 2. The reading magnifierof claim 1 wherein each of said tapered optical fibers has a diameter atthe large end of at least about 80 microns.
 3. The reading magnifier ofclaim 1 wherein the large end of said bundle is substantially parallelwith the flat small end of said bundle.
 4. The reading magnifier ofclaim 1 wherein the large end of said bundle has a convex sphericalsurface.
 5. The reading magnifier of claim 1 wherein the large end ofsaid bundle has a cylindrical surface.
 6. The reading magnifier of claim1 wherein said bundle of tapered optical fibers has a constant diameterportion extending between the large end and a tapered portion of saidfibers.
 7. The reading magnifier of claim 1 wherein said bundle oftapered optical fibers is characterized by a cone of light admittancethrough the large end that is skewed at an angle relative to a directionnormal to the flat small end.